(1) Field of the Invention
The present invention relates to a technology for improving a contrast offered by an image display device that employs a display panel such as a liquid crystal display (LCD) or a plasma display panel (PDP), and alleviating moiré occurring therein.
(2) Description of the Related Art
Image display devices employing a display panel such as an LCD or a PDP are widely prevailing as a display device to be included in a television. Since the television is simultaneously viewed by multiple viewers, it is requested to offer a sufficiently wide viewing angle. Furthermore, since the television is often viewed under a bright environment, it is requested to suppress the degradation in a contrast caused by convergence of outside environmental light (for example, room lighting) on the display panel (in other words, it is requested to improve a contrast to be ensured in a bright room).
Technologies for improving a contrast to be ensured in a bright room despite convergence of outside environmental light have been disclosed in, for example, Japanese Patent Application Laid-Open Publication Nos. 2005-338270 and 2006-189867.
Japanese Patent Application Laid-Open Publication No. 2005-338270 has disclosed an idea that: outside environmental light is intercepted by an array of trapezoidal lenses and wedged pieces providing an effect of light absorption; and the refractive indices of the lenses and wedged pieces respectively are controlled in order to fully reflect part of a light beam.
Japanese Patent Application Laid-Open Publication No. 2006-189867 has disclosed an idea that: outside environmental light is intercepted by a substrate made of a transparent resin material and an array of wedged black stripes; and the refractive indices of the substrate made of a transparent resin material and the wedged black stripes respectively are controlled in order to fully reflect part of a light beam.